Field strength measuring device



FIG. 1 is a rear perspective view of the ornamental design of field strength measuring device in accordance with the present invention;

FIG. 2 is a front perspective view of the ornamental design of the present invention;

FIG. 3 is a side view of the ornamental design of the present invention;

FIG. 4 is a top view of the ornamental design of the present invention; and,

FIG. 5 is a bottom view of the ornamental design of the present invention. 

The ornamental design for a field strength measuring device, as shown. 